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Physics Astrophysics Instrumentation and Methods for Astrophysics

astro-ph.IM Watch Instrumentation and Methods for Astrophysics

Wednesday 26 August

Instrumentation and Methods for Astrophysics

Best practices for obtaining astrometric observations from JWST (274) NIRCam data

Marco Micheli and Bryan J. Holler

The James Webb Space Telescope (JWST), with its near-infrared imager NIRCam, is capable of obtaining detections of small bodies down to what would correspond to a visual magnitude of about 31. However, the complexity of NIRCam introduces multiple subtle effects in the way the images are obtained, and they in turn affect the astrometric information that can be extracted from the images. In the following, we very briefly summarize these peculiarities, and provide some basic information on how to extract meaningful astrometric positions from NIRCam images.
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Instrumentation and Methods for Astrophysics

Anatomy of an extensive air shower: building an optimal radio emission calculation

Juan Ammerman-Yebra and Harm Schoorlemmer

Radio emission from particle air showers is one of the most promising detection techniques to achieve an experiment with a large exposure in ultra-high-energy astroparticle physics. In this regime, above $10^{17}$ eV, the detailed calculation of the radio emission from Monte Carlo particle showers is sufficiently CPU intensive that statistical studies and optimization problems remain largely out of reach. In this article we examine the characteristics of the longitudinal and lateral development of extensive air showers, and exploit them to obtain a fast evaluation of the associated radio emission. We introduce the Coherent Radio Emission from Positrons and Electrons in Showers (CREPES) algorithm, in which the particle distributions are precomputed once and the emission is subsequently obtained from them, yielding a gain in speed of more than three orders of magnitude while preserving the accuracy of the microscopic calculation.
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Instrumentation and Methods for Astrophysics

Simulating an imaging atmospheric radio telescope to observe cosmic gamma rays and cosmic neutrinos

Sebastian Achim Mueller, Anne Timmermans, Juan Ammerman-Yebra et al. (+1 more)

Observations of cosmic gamma~rays with energies above the 10$^{12}$ electronvolts (TeV) regime are often a direct probe of events where our theoretical predictions are challenged by extreme conditions. Because high energetic cosmic gamma-rays are rare, one needs collection areas with the size of soccer fields (10$^{5}$ m$^2$) or more to gather significant counting statistics in short time. The imaging atmospheric Cherenkov telescope detects cosmic gamma-rays in such large areas and currently offers the best reconstruction power for the cosmic particle's type, energy, and direction in particular. However, with only about 1,000 hours of dark and clear nights every year, the imaging atmospheric Cherenkov~telescope only has a duty cycle of about $12\%$. To overcome this limitation, we propose a novel imaging atmospheric radio telescope. By observing radio emission in the $10$ GHz regime from air showers, the imaging atmospheric radio telescope could observe 24/7, independent of the day night cycle, and almost independent of the weather. The novelty here is the high resolution imaging of the air shower's radio emission which might result in high resolution images as one finds them in imaging atmospheric Cherenkov~telescopes. We present a technique to simulate the image formation in the radio telescope using wave mechanics instead of conventional ray tracing. The imaging atmospheric radio telescope could increase our access more than eight-fold to an accurately reconstructed high energy gamma-ray-sky. Further, the imaging atmospheric radio telescope might also eight fold the observation power for cosmic neutrinos in the so called Earth-skimming technique.
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All authors Sebastian Achim Mueller, Anne Timmermans, Juan Ammerman-Yebra, Harm Schoorlemmer

Instrumentation and Methods for Astrophysics

RISTRETTO: Assembly and Testing of the Seven-spaxel, High-resolution, Diffraction-limited Spectrograph

Leonie Hoerner, Bruno Chazelas, Nathanaël Restori et al. (+24 more)

The RISTRETTO project aims at the direct detection of the reflected light of extra-solar planets to measure albedos and detect possible biosignatures, using the high-contrast / high-resolution method. We report on the assembly, lab-testing and on-sky testing of the seven-spaxel high-resolution single-mode spectrograph which was built ahead of the rest of the instrument. The spectrograph is a high resolution echelle spectrograph build for high spectral fidelity being uder vacuum and thermally controlled. Once the assembly has been completed we had the chance to test it on sky using OHP 1.52 m telescope using the PAPYRUS AO system for injection in our spectrograph.
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All authors Leonie Hoerner, Bruno Chazelas, Nathanaël Restori, Christophe Lovis, Nicolas Blind, Ludovic Genolet, Ian Hughes, Michael Sordet, Robin Schnell, Anthony Carvalho, Maddalena Bugatti, Adrien Crausaz, Samuel Rihs, Gilles Simond, Isaac Bernardino Dinis, David Ehrenreich, Emeline Bolmont, Christoph Mordasini, Martin Turbet, Angelie Alagao, Vincent Chambouleyron, Mathieu Motte, Arnaud Striffling, Francissco Oyarzun, Benoit Neichel, Jean-François Sauvage, Thierry Fusco

Instrumentation and Methods for Astrophysics

LP-Infinity: overcoming limits to the number of lifetime positions in the COS FUV channel

David J. Sahnow and Christian I. Johnson

Since the Cosmic Origins Spectrograph (COS) was installed on the Hubble Space Telescope (HST) in 2009, thousands of spectra have been collected with the Far Ultraviolet (FUV) channel. Due to the gain sag inherent in the cross delay line detector, regular adjustments to the positions of the spectra have been made, with the seventh and eighth becoming available to Guest Observers in October 2025. Recent improvements to models of the FUV channel, including more extensive optical modeling and better prediction and accommodation of detector gain sag, have allowed us to identify previously excluded locations on the detector for future use, thus requiring additional Lifetime Positions (LPs) to be defined. Since the onboard flight software limited the number of Lifetime Positions to eight, we developed a new method for implementing additional LPs to avoid dealing with the complications of reassigning previously used LPs. This novel strategy, dubbed LP-Infinity, allows an effectively unlimited number of LPs that is now constrained only by the available detector real estate, allowing COS to continue obtaining high-quality FUV spectra well into the 2030s. We discuss the conception, development and implementation of LP-Infinity, its initial use in Cycle 33, and the plans for future LPs starting in 2027.
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Instrumentation and Methods for Astrophysics · Cross-listed from astro-ph.GA

Recovering the effective impact parameters in integral-field absorption-line tomography

J. A. Hernández-Guajardo, L. F. Barrientos, C. Ledoux et al. (+3 more)

Integral-field-unit (IFU) spectroscopy of extended background sources, such as gravitational arcs, delivers many closely spaced absorption sightlines through the circumgalactic medium (CGM) of foreground galaxies. However, the source extent and smearing through the point spread function (PSF) cause each spaxel to integrate light from a region larger than itself. The usually adopted geometric spaxel centre is therefore not representative of where the absorbed flux originates. Informed by high-resolution imaging, we introduce a flux-contribution formalism that reconstructs the spatial origin of the flux in each spaxel by defining flux-weighted coordinates and impact parameters. Using a data-driven simulation built on a real gravitational-arc configuration, we show that spaxel centres are displaced from the flux-weighted positions by $|\Delta\mathbf{x}| \propto \theta_{\rm PSF}(1-f)$, with $f$ the spaxel-source overlap fraction, and that the resulting impact-parameter bias scales with the lensing magnification as $\mu^{-1/2}$. These offsets are largest for off-arc spaxels and flatten the radial column-density profiles. They also inject a coherent geometry-driven scatter that mimics intrinsic CGM structure and that is removed neither by a tighter spaxel selection nor by a finer spatial binning. For identical uncertainties, the spaxel-centre coordinates leave residuals of about twice the noise level ($\chi^2_\nu \sim 4$), whereas the flux-weighted coordinates recover the input profile to within the uncertainties ($\chi^2_\nu \sim 1$) and remain robust to a PSF misspecification of $\pm 10\%$. The method we propose provides a better-motivated and readily adoptable framework for tomographic studies, whether as the primary analysis or as a robustness check on spaxel-centre results.
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All authors J. A. Hernández-Guajardo, L. F. Barrientos, C. Ledoux, N. Tejos, E. J. Johnston, P. Anshul

Tuesday 25 August

Instrumentation and Methods for Astrophysics

Engineering of titanium transition edge sensor wafers for the BA4-90/150 receiver of BICEP Array

A.Patel, P. A. R. Ade, Z. Ahmed et al. (+83 more)

BA4-90/150, the fourth receiver to be deployed in the BICEP Array (BA) series, is a dichroic 90/150 GHz instrument targeting the frequency space where sensitivity to the CMB polarization is maximized. The receiver will be deployed in the 2026-2027 austral summer, and is set to position BA to achieve exceptionally precise measurements of cosmic microwave background (CMB) polarization and strengthen constraints on inflationary models. Recent measurements in existing BA receivers suggest that unexpectedly high loop gain in the titanium (Ti) transition edge sensors (TESs) produces excess high-frequency noise that is consequently aliased down into the science band through the time-division multiplexed readout. To reduce the loop gain, we fabricated and tested prototype Ti TES wafers containing 16 modified detector architectures designed to broaden the superconducting transition and reduce the transition steepness (alpha). We present detector performance results, which will directly inform the final integrated wafer now being designed for full receiver commissioning.
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All authors A.Patel, P. A. R. Ade, Z. Ahmed, M. Amiri, D. Barkats, R. Basu Thakur, C. A. Bischoff, D. Beck, J. J. Bock, V. Buza, B. Cantrall, J. R. Cheshire IV, J. Connors, J. Cornelison, M. Crumrine, A. J. Cukierman, E. Denison, L. Duband, M. A. Echter, M. Eiben, B. D. Elwood, S. Fatigoni, J. P. Filippini, A. Fortes, M. Gao, C. Giannakopoulos, N. Goeckner-Wald, D. C. Goldfinger, S. Gratton, J. A. Grayson, A. Greathouse, P. K. Grimes, M. Halpern, S. Henderson, T. D. Hoang, J. Hubmayr, H. Hui, K. D. Irwin, M. Izquierdo Poza, J. H. Kang, K. S. Karkare, S. Kefeli, J. M. Kovac, C. Kuo, K. Lasko, K. Lau, M. Lautzenhiser, T. Liu, S. C. Mackey, N. Maher, K. G. Megerian, L. Minutolo, L. Moncelsi, Y. Nakato, H. T. Nguyen, R. O'Brient, S. N. Paine, M. A. Petroff, A. R. Polish, T. Prouve, C. Pryke, C. D. Reintsema, T. Romand, M. Salatino, A. Schillaci, B. Schmitt, B. Singari, A. Soliman, T. St. Germaine, A. Steiger, B. Steinbach, R. Sudiwala, K. L. Thompson, C. Tucker, A. D. Turner, C. Vergès, A. G. Vieregg, A. Wandui, A. C. Weber, J. Willmert, W. L. K. Wu, H. Yang, C. Yu, L. Zeng, C. Zhang, S. Zhang

Instrumentation and Methods for Astrophysics

Spatially Scanned STIS Spectra of the Exoplanet Host Star 55 Cnc

D. E. Welty, J. D. Lothringer, D. K. Sing et al. (+3 more)

We discuss the analysis of two sets of optical/near-IR spectra of the exoplanet host star 55 Cnc, obtained with the Space Telescope Imaging Spectrograph (STIS) and grating G750L in spatial scanning mode, in order to assess the performance of that relatively new observing mode for studies of transiting exoplanets. Standard pipeline reductions of the CCD spectral images were augmented by custom procedures for removing both cosmic rays and the strong fringing seen at wavelengths longer than 7000 A. Both total ("white-light") fluxes and the fluxes for narrower wavelength intervals were extracted from the processed spectral images. Apart from slight ($\sim$400 ppm) orbit-to-orbit offsets between the relative fluxes in each set, the patterns exhibited by the flux values within each orbit are very similar. The systematic differences in the fluxes are somewhat smaller than those seen in STIS spectra of 55 Cnc obtained in "stare mode", where the CCD is deliberately saturated at a fixed pointing. A parameterized detrending method similar to those commonly used to remove instrumental effects from time series observations of exoplanet host stars was then applied to the extracted fluxes. For the total fluxes, the scatter about the detrending models is $\sim$30-40 ppm – comparable to the best precision previously obtained for time series photometry with HST – but is somewhat larger for narrower wavelength bins. The depth of the transit of the super-Earth 55 Cnc e ($\sim$450 ppm for the total flux) is consistent with previous values. Both the scan-mode and the stare-mode observations of 55 Cnc e appear to indicate an unexpected (and variable?) increase in the transit radius Rp/Rs between 0.55 and 1.0 $\mu$m. While these data are somewhat limited, they do suggest that spatial scanning with the STIS CCD can provide high-quality optical/near-IR spectra of the brighter exoplanet hosts. (edited)
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All authors D. E. Welty, J. D. Lothringer, D. K. Sing, A. M. Jones, A. Riley, C. R. Proffitt

Instrumentation and Methods for Astrophysics

Deep Learning-Based Coarse Alignment and Cophasing of a Distributed-Aperture Telescope. Application to the Small ExoLife Finder (SELF)

N. Arteaga-Marrero, J. Iborra-Luis, A. Padrón-Brito et al. (+1 more)

The ExoLife Finder (ELF), a 35–50-meter-class Fizeau interferometric telescope, was designed to detect biosignatures on exoplanets through direct imaging. The Small ExoLife Finder (SELF), a 3.5-meter prototype, serves as a testbed for the innovative technologies required for such a facility. A key challenge is the precise cophasing of its distributed aperture, where the optical path differences between subapertures must remain below a small fraction of the operating wavelength. This work investigates convolutional neural networks (CNNs) to estimate alignment errors directly from focal-plane images, enabling fast, data-driven coarse alignment to the few-micrometer level. A supervised regression framework was developed using a custom CNN to model the nonlinear mapping between subaperture misalignments and focal-plane intensity distributions. Training and validation datasets were generated from high-fidelity optical simulations of the simplified SELF system. Gaussian-noise augmentation was used to assess robustness, and several established CNN architectures were evaluated for comparison. The proposed approach reconstructed piston and tilt misalignments across all mirror pairs, demonstrating that focal-plane interference patterns can be exploited for alignment estimation. The custom CNN provided a favorable balance between estimation performance, robustness, and computational efficiency, with millisecond-scale inference times. A trade-off between performance and noise robustness was identified, with noise augmentation improving reconstruction at low signal-to-noise ratios but reduced performance under near noise-free conditions. These results demonstrate the feasibility of data-driven focal-plane wavefront sensing for distributed-aperture telescopes and provide a basis for autonomous, computationally efficient cophasing strategies for future high-resolution interferometric systems.
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All authors N. Arteaga-Marrero, J. Iborra-Luis, A. Padrón-Brito, J. Kuhn

Instrumentation and Methods for Astrophysics · Cross-listed from astro-ph.SR

ABYSS. IV. Identifying signatures of stellar youth in APOGEE spectra

Valentina Bonilla Villalobos, Marina Kounkel, Joseph Mullen et al. (+9 more)

We develop a convolutional neural network classifier that performs spectroscopic identification of stellar youth (<40 Myr) in APOGEE spectra. This classifier is sensitive to several youth-related features, including rotational broadening, which is common in younger stars, and to several discrete lines that appear to be indicative of a very spotted photosphere. The model is successful at identifying youth across a wide range of stars, achieving its strongest performance at discriminating young M and K dwarfs, while maintaining useful discriminatory power for hotter stars as well. This work enables more robust separation of pre-main-sequence stars from more evolved sources in the field even when they have comparable Teff and log(g), providing a reliable means to substantially reduce contamination in photometrically selected YSO candidates. In addition to constructing a classifier for APOGEE spectra, we also perform classification of young stars in optical BOSS spectra.
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All authors Valentina Bonilla Villalobos, Marina Kounkel, Joseph Mullen, Eleonora Zari, Alexandre Roman-Lopes, Keivan Stassun, Ricardo López-Valdivia, Jinyoung S. Kim, Mojgan Aghakhanloo, Facundo Pérez Paolino, Jonathan C. Tan, Jesús Hernández

Instrumentation and Methods for Astrophysics

Capra: Scalable HEALPix-Native Intensity Reconstruction for High-Resolution IMAP Analyses

Nikola Bukowiecka, Daniel B. Reisenfeld and Maciej Bzowski

We present Capra, a HEALPix-native pipeline for reconstructing all-sky energetic neutral atom (ENA) intensity maps from the NASA Interstellar Boundary Explorer (IBEX) and Interstellar Mapping and Acceleration (IMAP) missions' event-counting data. Capra produces two products: (1) a baseline boresight-assigned map, and (2) an optional smoothed map on the HEALPix grid. This produces smooth, physically interpretable maps with consistent resolution changes and reference-frame transformations. The smoothed Capra maps recover the large-scale ENA morphology while reducing sampling-driven mottling and strip-like artifacts. Relative comparison with the Theseus reconstruction shows broadly consistent large-scale structure, with the discrepancies reflecting differences in reconstruction methods, rather than major morphological discrepancies. We verify invariance (preservation) of count numbers, rates, and intensities across tessellations under coordinate transformations, and demonstrate numerical convergence up to HEALPix resolution Nside = 64 for a representative dataset. We show that thread-based parallelism performance exhibits approximately linear strong scaling, with bounded memory usage, enabling efficient high-resolution reconstruction and making Capra well-suited for high-resolution IMAP reconstruction.
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Instrumentation and Methods for Astrophysics

TESSExtractor: A web-based interactive tool for light-curve visualisation and period estimation using TESS full-frame images

Javier Serna, Jesús Hernández, Sean P. Matt et al. (+23 more)

We present a user-friendly web application that allows users to extract, visualise, and interact with TESS light-curves (LCs) from full-frame images. The service works for any star identified in the TIC database or using stellar coordinates. TESSExtractor performs photometry using a circular aperture centred on the object of interest, with a sky annulus for background subtraction. The application also uses cotrending basis vectors provided by TESS to correct photometry for possible systematic effects. The Lomb-Scargle Periodogram is used to obtain periods from the LC. The TESSExtractor's website offers an intuitive interface for scientific and educational purposes and is publicly available at https://www.tessextractor.app. This tool simplifies the analysis of TESS LCs and provides valuable insight for researchers seeking to extract and analyse TESS data for a variety of scientific goals (e.g., stellar rotation, activity, transient detection, asteroseismology, or simply detection of planetary transits or stellar companions, among others). TESS provides insights into our understanding of time-domain astrophysics, and TESSExtractor provides an accessible and intuitive web interface for scientific exploitation of TESS data. We demonstrate that TESSExtractor produces LCs of sufficient quality for both quantitative and morphological time-domain studies.
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All authors Javier Serna, Jesús Hernández, Sean P. Matt, Giovanni Pinzón, Astaroth Elizabethson, Jorge Martínez-Palomera, Carlos G. Román-Zúñiga, Sergio Sánchez-Sanjuán, Jaime Morice, Thanawuth Thanathibodee, Margarita Pereyra, Mauricio Tapia, Alejandro García-Varela, Juan F. Cabrera-García, Marcelo Jaque Arancibia, María Gracia Batista, Ricardo López-Valdivia, Raúl Michel, Ezequiel Manzo-Martínez, Keivan G. Stassun, Cesar Briceño, Sydney Robertson, Tanay Ayiliath, David Fernández, Fabián Ahumada, Alejandro Alfonso

Instrumentation and Methods for Astrophysics

CCAT: The Prime-Cam Instrument for the Fred Young Submillimeter Telescope – Overview and Status

Eve M. Vavagiakis, Yuhan Wang, Lawrence T. Lin et al. (+32 more)

Prime-Cam is a first-generation science instrument for the CCAT Observatory's six-meter aperture Fred Young Submillimeter Telescope (FYST), under construction at an elevation of 5600 m on Cerro Chajnantor in Chile's Atacama Desert. Prime-Cam will deliver over ten times greater mapping speed at submillimeter wavelengths than current facilities for unprecedented broadband and spectroscopic measurements in windows between 1.4 – 0.3 mm (220 – 850 GHz). When fully populated, Prime-Cam will field over 100,000 kinetic inductance detectors across seven independently optimized instrument modules. With Prime-Cam, the CCAT Collaboration will address a suite of science goals, from Big Bang cosmology, to galaxy evolution and star formation over cosmic time. Prime-Cam is scheduled for integration in FYST in late 2026, followed by a year of early science observations with the 280 and 350 GHz instrument modules. We discuss the design and in-lab testing of the 1.8-m diameter Prime-Cam receiver and 280 GHz instrument module, and give an update on deployment status and early science plans.
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All authors Eve M. Vavagiakis, Yuhan Wang, Lawrence T. Lin, Manuel Aravena, Jason E. Austermann, Frank Bertoldi, James Burgoyne, Victoria Butler, Scott Chapman, Steve K. Choi, Dongwoo Chung, Abigail Crites, Ankur Dev, Cody J. Duell, Michel Fich, Laura Fissel, Rodrigo G. Freundt, Eliza Gazda, Anthony I. Huber, Doug Johnstone, Ben Keller, Paul Malachuk, Alicia Middleton, Jenna Moore, Michael D. Niemack, Thomas Nikola, Yoko Okada, Darshan A. Patel, Tilak M. Patel, Dominik A. Riechers, Douglas Scott, Gordon J. Stacey, Benjamin J. Vaughan, Samantha Walker, Ruixuan Xie

Instrumentation and Methods for Astrophysics

A Singular Value Decomposition Framework for Jovian Radio Emissions from Parker Solar Probe

Evan Wille, Zack Li, Marc Pulupa et al. (+3 more)

Jovian decametric and hectometric radio emissions provide critical insights into Jupiter's magnetospheric dynamics and its electrodynamic coupling with Io. Across 21 perihelion encounters since its first light in 2018, the Parker Solar Probe mission has repeatedly recorded high-resolution radio and plasma wave data near closest approach, as a result serving as a long-term distant observer of the Jovian system. However, extracting these relatively faint planetary signals from the continuous solar wind background presents a significant analytical challenge, as the data is routinely saturated by quasi-thermal plasma noise, spacecraft instrumental interference, and solar bursts. To overcome these observational barriers, we present a generalized empirical pipeline that utilizes Singular Value Decomposition coupled with a deterministic, dual-stage noise filtering process. By converting dynamic spectra into a periodic, phase-folded reference frame, this model isolates structured Jovian emissions from the stochastic heliospheric background, demonstrating empirical Signal-to-Noise Ratio improvements of $1.54 \pm 0.11$ dB, reaching up to $3.32$ dB. Additionally, a secondary “Eigenfaces” matrix factorization is applied to identify long-term global morphological trends and serve as a detection method for future Jovian emissions. This automated mathematical framework extracts transient planetary signals without relying on localized spatial constraints, establishing the viability of PSP as a Jovian radio observatory.
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All authors Evan Wille, Zack Li, Marc Pulupa, Leon V.E. Koopmans, Philippe Zarka, Stuart Bale

Instrumentation and Methods for Astrophysics

Study of Vibrations at SOAR

Andrei Tokovinin

The 4.1-m Southern Astrophysics Research (SOAR) telescope in Chile resembles larger optical telescopes by its thin actively controlled primary mirror, built-in tip-tilt correction, lightweight structure, and adaptive optics (AO) turbulence correction. The non-stationary vibration of the SOAR optical axis with a frequency of 50 Hz and an amplitude reaching 20-30 mas has been detected by the AO system, degrading the quality of optical speckle interferometric data. Accelerometers revealed that the 50 Hz tremor, driven by an external source, propagates within telescope structure and is strongly amplified by the response of the fast tip-tilt mirror servo system, producing characteristic elliptical beam path. The AO system also evidenced periodic components at 47 Hz in the defocus (matching the frequency of fans in electronic racks and computers) and at ~65 Hz in the astigmatism. The latter is associated with structural resonances of the SOAR primary mirror support, apparently excited by the wind. Periodic tracking errors with typical frequencies of 0.5-2.5 Hz are mostly caused by periodic errors of the encoders, depending on their alignment, and can be amplified by the mount servo at fast tracking rates. Vibration characterization at SOAR informs similar studies at other telescopes.
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Instrumentation and Methods for Astrophysics · Cross-listed from astro-ph.SR

EncoTESS: Age-Sensitive Encodings from Raw TESS Light Curves

Phil R. Van-Lane, Joshua S. Speagle, Ryan Cloutier et al. (+3 more)

Main sequence stars of spectral types late F through M exhibit systematic variability in photometric light curves, particularly when they are young. Rotational modulation of starspots manifests as quasi-sinusoidal variability, which enables the measurement of rotation periods. Variability can also be stochastic, as in stellar flaring. However, since measurements of stochastic processes depend on the time of observation, they are typically noisier. Considering that different manifestations of variability have unique observational nuances, models that naturally unify these are incredibly useful for stellar characterization. Towards this goal, we have developed EncoTESS: a Time Series Foundation Model (TSFM) trained on a subset of TESS 2-min light curves. EncoTESS is specifically designed to handle the observational noise, heteroskedastic measurements, irregular sampling, and large data gaps common to TESS data. It is also ~1% of the size of a typical literature TSFM, so can be run easily on a modern laptop. EncoTESS encodes light curves into a fixed-size latent parameter space, which can be used to infer physical stellar properties and recovers light curve summary statistics well. EncoTESS outperforms rotation period and variability amplitude as age indicators for stars that have not converged onto the slow rotator sequence yet; broadly these include K and M stars less than ~100 Myr, and M stars less than ~1 Gyr. We focus on age inference as an application of EncoTESS in this work, but other downstream tasks such as stellar classification could also be explored. The architecture of EncoTESS enables its future extension to TESS light curves of all cadences, and additional surveys such as Kepler and the upcoming PLATO mission. The core EncoTESS framework and library of encodings produced for the stars used in this work are publicly available at https://github.com/philvanlane/encotess.
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All authors Phil R. Van-Lane, Joshua S. Speagle, Ryan Cloutier, Christopher A. Theissen, Gwendolyn M. Eadie, Ilay Kamai

Instrumentation and Methods for Astrophysics · Cross-listed from astro-ph.CO

Quantifying the systematic impact of differential beam response on the BICEP CMB polarization data from 2016 through 2024

B. D. Elwood, P. A. R. Ade, Z. Ahmed et al. (+83 more)

As cosmic microwave background (CMB) polarization experiments, including BICEP3, BICEP Array, and future BICEP experiments, achieve ever-deeper polarization maps in search of primordial B-modes sourced from inflation, constraining instrumental systematics below statistical uncertainties becomes progressively more challenging. Since polarimetry in the BICEP telescopes is performed by pair-differencing co-located, orthogonally polarized detectors, differential beam response leads to temperature-to-polarization ($T \rightarrow P$) leakage, introducing a potential systematic bias on the inferred tensor-to-scalar ratio $r$. To mitigate this leakage, the lowest-order beam mismatch modes are filtered out of the CMB polarization maps through deprojection; however, residual undeprojected modes remain. To quantify this residual contamination, we perform dedicated in situ far-field beam measurements of the BICEP receivers during austral-summer calibration campaigns. We quantify the systematic impact of the undeprojected residuals with a specialized set of timestream simulations based on the measured per-detector beams. These "beam measurement-informed simulations" yield an estimate of the false polarized signal sourced by the undeprojected residuals. We summarize the beam measurements relevant to the BK24 data release and present preliminary residual-leakage results for BICEP3 at 95 GHz. For BICEP3 over 2016-2024, deprojecting all six standard templates together with readout-crosstalk templates and their radially smoothed counterparts reduces the equivalent-$r$ leakage amplitude from $\rho=(4.5\pm0.7)\times10^{-3}$ to $(1.12\pm0.06)\times10^{-3}$. We further describe an ongoing program to extend the deprojection basis beyond its historical six modes, guided by a forward optical model that relates candidate leakage modes to perturbations of physical instrument parameters.
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All authors B. D. Elwood, P. A. R. Ade, Z. Ahmed, M. Amiri, D. Barkats, R. Basu Thakur, C. A. Bischoff, D. Beck, J. J. Bock, V. Buza, B. Cantrall, J. R. Cheshire IV, J. Connors, J. Cornelison, M. Crumrine, A. J. Cukierman, E. Denison, L. Duband, M. A. Echter, M. Eiben, S. Fatigoni, J. P. Filippini, A. Fortes, M. Gao, C. Giannakopoulos, N. Goeckner-Wald, D. C. Goldfinger, S. Gratton, J. A. Grayson, A. Greathouse, P. K. Grimes, M. Halpern, S. Henderson, T. D. Hoang, J. Hubmayr, H. Hui, K. D. Irwin, M. Izquierdo Poza, J. H. Kang, K. S. Karkare, S. Kefeli, J. M. Kovac, C. Kuo, K. Lasko, K. Lau, M. Lautzenhiser, T. Liu, S. C. Mackey, N. Maher, K. G. Megerian, L. Minutolo, L. Moncelsi, Y. Nakato, H. T. Nguyen, R. O'Brient, S. N. Paine, A. Patel, M. A. Petroff, A. R. Polish, T. Prouve, C. Pryke, C. D. Reintsema, T. Romand, M. Salatino, A. Schillaci, B. Schmitt, B. Singari, A. Soliman, T. St. Germaine, A. Steiger, B. Steinbach, R. Sudiwala, K. L. Thompson, C. Tucker, A. D. Turner, C. Vergès, A. G. Vieregg, A. Wandui, A. C. Weber, J. Willmert, W. L. K. Wu, H. Yang, C. Yu, L. Zeng, C. Zhang, S. Zhang

Instrumentation and Methods for Astrophysics

Status of BICEP Array and Integration of the 220/270 GHz Receiver

A. Steiger, P. A. R. Ade, Z. Ahmed et al. (+83 more)

Measurements of the polarization of the cosmic microwave background are critical for modern cosmology as they constrain the physics of the early universe and cosmic inflation. BICEP Array is using a series of small-aperture polarimeters located at the South Pole to measure this signal with a projected uncertainty on the tensor-to-scalar ratio r of approximately 0.001 by 2034. The 30/40 GHz receiver and the 150 GHz receiver have been observing the cosmic microwave background for multiple years, and data from these receivers will be included in the next published BICEP analysis result which includes all data taken through 2024. The 220/270 GHz receiver is partially completed with seven out of twelve detector modules installed, and is planned to be filled with five additional modules prior to the 2027 observation season. Finishing this receiver is a top priority for BA as the science goals of the experiment require the dust foreground cleaning this receiver will enable. On-site characterization efforts for this receiver from the 2025-26 austral summer show satisfactory spectroscopy, beam pointing, and 220 GHz efficiency, while the 270 GHz efficiency is an active area of work.
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All authors A. Steiger, P. A. R. Ade, Z. Ahmed, M. Amiri, D. Barkats, R. Basu Thakur, C. A. Bischoff, D. Beck, J. J. Bock, V. Buza, B. Cantrall, J. R. Cheshire IV, J. Connors, J. Cornelison, M. Crumrine, A. J. Cukierman, E. Denison, L. Duband, M. A. Echter, M. Eiben, B. D. Elwood, S. Fatigoni, J. P. Filippini, A. Fortes, M. Gao, C. Giannakopoulos, N. Goeckner-Wald, D. C. Goldfinger, S. Gratton, J. A. Grayson, A. Greathouse, P. K. Grimes, M. Halpern, S. Henderson, T. D. Hoang, J. Hubmayr, H. Hui, K. D. Irwin, M. Izquierdo Poza, J. H. Kang, K. S. Karkare, S. Kefeli, J. M. Kovac, C. Kuo, K. Lasko, K. Lau, M. Lautzenhiser, G. Liu, S. C. Mackey, N. Maher, K. G. Megerian, L. Minutolo, L. Moncelsi, Y. Nakato, H. T. Nguyen, R. O'Brient, S. N. Paine, A. Patel, M. A. Petroff, A. R. Polish, T. Prouve, C. Pryke, C. D. Reintsema, T. Romand, M. Salatino, A. Schillaci, B. Schmitt, B. Singari, A. Soliman, T. St. Germaine, B. Steinbach, R. Sudiwala, K. L. Thompson, C. Tucker, A. D. Turner, C. Vergès, A. G. Vieregg, A. Wandui, A. C. Weber, J. Willmert, W. L. K. Wu, H. Yang, C. Yu, L. Zeng, C. Zhang, S. Zhang

Instrumentation and Methods for Astrophysics

Optics and broadband anti-reflection coatings for the BA4-90/150 receiver

A. R. Polish, P. A. R. Ade, Z. Ahmed et al. (+84 more)

The BICEP Array telescopes search for primordial B-mode polarization from inflationary gravitational waves. This signal is exceedingly faint, demanding excellent map depth and systematics control. The new BA4-90/150 receiver introduces a wide 80-169GHz dichroic band, requiring upgrades throughout the optics chain to reduce loss, reflections, and thermal loading. We developed improved anti-reflection (AR) coatings for our HMPE window, HDPE lenses, and nylon infrared filter, extending our AR technology to span more than an octave of bandwidth. The thermal filtering scheme and several mechanical elements were also updated to further suppress optical loss, reflections, and beam truncation. We aim to build on the proven success of deployed BICEP Array (BA) telescopes to produce a new small aperture instrument with the lowest optical systematics to date.
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All authors A. R. Polish, P. A. R. Ade, Z. Ahmed, M. Amiri, D. Barkats, R. Basu Thakur, C. A. Bischoff, D. Beck, J. J. Bock, V. Buza, B. Cantrall, J. R. Cheshire IV, J. Connors, J. Cornelison, M. Crumrine, A. J. Cukierman, E. Denison, L. Duband, M. A. Echter, M. Eiben, B. D. Elwood, S. Fatigoni, J. P. Filippini, A. Fortes, M. Gao, C. Giannakopoulos, N. Goeckner-Wald, D. C. Goldfinger, S. Gratton, J. A. Grayson, A. Greathouse, P. K. Grimes, M. Halpern, S. Henderson, T. D. Hoang, J. Hubmayr, H. Hui, K. D. Irwin, M. Izquierdo Poza, J. H. Kang, K. S. Karkare, S. Kefeli, J. M. Kovac, C. Kuo, K. Lasko, K. Lau, M. Lautzenhiser, T. Liu, S. C. Mackey, N. Maher, K. G. Megerian, L. Minutolo, L. Moncelsi, Y. Nakato, H. T. Nguyen, R. O'Brient, S. N. Paine, A. Patel, M. A. Petroff, T. Prouve, C. Pryke, C. D. Reintsema, P. J. Rioles, T. Romand, M. Salatino, A. Schillaci, B. Schmitt, B. Singari, A. Soliman, T. St. Germaine, A. Steiger, B. Steinbach, R. Sudiwala, K. L. Thompson, C. Tucker, A. D. Turner, C. Vergès, A. G. Vieregg, A. Wandui, A. C. Weber, J. Willmert, W. L. K. Wu, H. Yang, C. Yu, L. Zeng, C. Zhang, S. Zhang

Instrumentation and Methods for Astrophysics

Advanced Time-Division Multiplexed Readout Chain for the BICEP Array 90/150 GHz Receiver

B. Cantrall, P. A. R. Ade, Z. Ahmed et al. (+89 more)

This work presents the current performance of the advanced time-division multiplexed (TDM) readout chain for the BICEP Array 90/150 GHz receiver. BA4-90/150, scheduled for deployment to the South Pole in 2026–27, will use photon-noise-limited, feedhorn-coupled transition edge sensor detectors and an upgraded DC SQUID-based TDM system to map the cosmic microwave background. This new TDM system mitigates readout-induced systematics that are beginning to emerge above the noise floor of the most sensitive maps produced by the BICEP collaboration. Improvements include faster, fully differential SQUID designs, higher TES signal amplification, reduced crosstalk, and hierarchical row-addressing that reduces wiring required for row switching. Measurements made through legacy single-ended warm readout electronics show the upgraded cryogenic readout chain performs as well as or better than the TDM system currently fielded on the BICEP experiment. New warm electronics currently in development at SLAC National Accelerator Laboratory will provide matched fully differential circuits and higher bandwidth, reducing RF susceptibility and aliased noise contributions. On-sky demonstration of this technology will establish a new low-noise, high-bandwidth TDM architecture for future CMB observatories.
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All authors B. Cantrall, P. A. R. Ade, Z. Ahmed, M. Amiri, D. Barkats, R. Basu Thakur, C. A. Bischoff, D. Beck, J. J. Bock, V. Buza, J. R. Cheshire IV, J. Connors, J. Cornelison, M. Crumrine, A. J. Cukierman, E. Denison, W. B. Doriese, L. Duband, M. Durkin, M. A. Echter, M. Eiben, B. D. Elwood, S. Fatigoni, J. P. Filippini, A. Fortes, J. Gard, M. Gao, C. Giannakopoulos, N. Goeckner-Wald, D. C. Goldfinger, S. Gratton, J. A. Grayson, A. Greathouse, P. K. Grimes, G. Haller, M. Halpern, S. Henderson, T. D. Hoang, J. Hubmayr, H. Hui, K. D. Irwin, M. Izquierdo Poza, J. H. Kang, K. S. Karkare, S. Kefeli, J. M. Kovac, C. Kuo, K. Lasko, K. Lau, M. Lautzenhiser, T. Liu, S. C. Mackey, N. Maher, K. G. Megerian, L. Minutolo, L. Moncelsi, Y. Nakato, H. T. Nguyen, R. O'Brient, S. N. Paine, A. Patel, M. A. Petroff, A. R. Polish, T. Prouve, C. Pryke, C. D. Reintsema, T. Romand, M. Salatino, L. Sapozhnikov, A. Schillaci, B. Schmitt, R. Shi, B. Singari, A. Soliman, T. St. Germaine, A. Steiger, B. Steinbach, R. Sudiwala, K. L. Thompson, C. Tucker, A. D. Turner, C. Vergès, A. G. Vieregg, A. Wandui, A. C. Weber, J. Willmert, W. L. K. Wu, H. Yang, C. Yu, L. Zeng, C. Zhang, S. Zhang

Instrumentation and Methods for Astrophysics

Optical characterization of the BICEP array 150 and 220/270GHz CMB polarimeters in the 2026 season

M. Izquierdo Poza, P. A. R. Ade, Z. Ahmed et al. (+83 more)

BICEP Array (BA) is the current-generation instrument in the BICEP series of small-aperture, on-axis refracting telescopes at the South Pole, designed to constrain the tensor-to-scalar ratio $r$ through degree-scale measurements of B-mode polarization in the cosmic microwave background (CMB). As BA pushes to deeper sensitivity, control of instrumental systematics, and beam shape mismatch between the co-located orthogonally polarized detectors in particular, has become an increasingly important factor in translating raw sensitivity into a robust constraint on $r$. In these proceedings we report on the 2026 far field beam mapping (FFBM) campaign, which used a thermal chopped source to characterize the BA2 (150~GHz) and BA3 (220/270~GHz) beams. We fit two-dimensional elliptical Gaussians to each detector's beam, derive per-pair differential parameters (differential pointing, beamwidth, and ellipticity). The resulting high-signal-to-noise array-averaged beam maps are used to compute the beam window function $B_l$ for the power spectrum analysis, while the individual per-detector beams feed dedicated beam convolution simulations used to validate the temperature-to-polarization (T$\rightarrow$ P) deprojection procedure. After correcting for the chopper aperture, the recovered beamwidths follow the expected $\lambda/D$ ordering. We also describe two pipeline improvements carried out during the 2026 campaign: an out-and-back jackknife for noise quantification and an elnod-based gain calibration.
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All authors M. Izquierdo Poza, P. A. R. Ade, Z. Ahmed, M. Amiri, D. Barkats, R. Basu Thakur, C. A. Bischoff, D. Beck, J. J. Bock, V. Buza, B. Cantrall, J. R. Cheshire IV, J. Connors, J. Cornelison, M. Crumrine, A. J. Cukierman, E. Denison, L. Duband, M. A. Echter, M. Eiben, B. D. Elwood, S. Fatigoni, J. P. Filippini, A. Fortes, M. Gao, C. Giannakopoulos, N. Goeckner-Wald, D. C. Goldfinger, J. A. Grayson, A. Greathouse, P. K. Grimes, M. Halpern, S. Henderson, T. D. Hoang, J. Hubmayr, H. Hui, K. D. Irwin, M. Izquierdo Poza, J. H. Kang, K. S. Karkare, S. Kefeli, J. M. Kovac, C. Kuo, K. Lasko, K. Lau, M. Lautzenhiser, T. Liu, S. C. Mackey, N. Maher, K. G. Megerian, L. Minutolo, L. Moncelsi, Y. Nakato, H. T. Nguyen, R. O'Brient, S. N. Paine, A. Patel, M. A. Petroff, A. R. Polish, T. Prouve, C. Pryke, C. D. Reintsema, T. Romand, M. Salatino, A. Schillaci, B. Schmitt, B. Singari, A. Soliman, T. St. Germaine, A. Steiger, B. Steinbach, R. Sudiwala, K. L. Thompson, C. Tucker, A. D. Turner, C. Vergès, A. G. Vieregg, A. Wandui, A. C. Weber, J. Willmert, W. L. K. Wu, H. Yang, C. Yu, L. Zeng, C. Zhang, S. Zhang

Instrumentation and Methods for Astrophysics

Connecting Granulation and Magnetic Activity in Radial Velocities: The Next Breakthrough for High-Precision Spectroscopy

Ancy Anna John, Khaled Al Moulla, Federica Rescigno et al. (+5 more)

Stellar variability has become the dominant limitation to achieving the radial velocity (RV) precision required for the detection and characterization of Earth-like exoplanets. While significant progress has been made in mitigating the effects of oscillations and magnetic activity, convective granulation and its interaction with stellar magnetic fields remain among the least understood sources of RV variability. To address these challenges, we organized the splinter session `Connecting Granulation and Magnetic Activity in Radial Velocities: The Next Breakthrough for High-Precision Spectroscopy' at Cool Stars 23. The session brought together researchers working on observations, numerical simulations, and data-driven techniques to discuss the current understanding of granulation-driven RV signals and identify the most promising directions for future progress. Through invited and contributed talks, followed by community discussions, participants emphasized the importance of combining physically motivated models with data-driven approaches, developing standardized benchmark datasets, and validating simulations against high-quality observations across a range of stellar types. The discussions also highlighted the need for coordinated observing strategies, improved characterization of individual spectral lines, and physically informed line-by-line analyses to disentangle convective and magnetic signals. This contribution summarises the scientific discussions and community perspectives that emerged during the session and outlines the key challenges that must be addressed to reach the sub-40 cm/s precision required for the next generation of RV planet searches.
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All authors Ancy Anna John, Khaled Al Moulla, Federica Rescigno, Carmen San Nicolas Martinez, Andrew Collier Cameron, Thomas G. Wilson, Nadège Meunier, Sophia Sulis

Instrumentation and Methods for Astrophysics · Cross-listed from hep-ex

Cosmic muon arrival directions as a source of entropy

Deepak Samuel

We demonstrate, for the first time, that the arrival directions of cosmic-ray muons from a muon telescope provide a measurable source of physical entropy. Using six months of data collected from a muon telescope, the local zenith and azimuth angles were used for randomness extraction. The result of this study show that each cosmic muon track from our detector can generate upto 4 bits with an entropy of 0.999182 bits/bit with a maximum bit rate of roughly 650 bits/s which can possibly be enhanced by improving the detector size and angular resolution. The suggested technique can be potentially used as a random number generator required for closing the settings-independence loophole in the tests for violations of Bell's inequality. The data acquisition, data reduction, and conditioning algorithms are discussed in detail.
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Instrumentation and Methods for Astrophysics · Cross-listed from astro-ph.SR

Improving the Physical Interpretability of Gaussian Processes in Stellar Activity Modeling: A Study Case on Photometric Variability Among Stellar Clusters

Leslie Moranta, Jonathan Gagné, Jacqueline K. Faherty et al. (+12 more)

Gaussian Processes (GPs) are widely used to model stellar variability in photometric surveys, but a statistically successful fit does not guarantee that the inferred hyperparameters correspond to physically meaningful stellar properties. This is especially important for young, active stars, whose TESS light curves contain evolving spots, harmonics, and non-sinusoidal variability. We use stellar rotation as a case study to examine when the period hyperparameter of a quasi-periodic GP can be interpreted as a physical rotation period. We introduce a regularized GP likelihood that reweights the covariance-complexity term in the marginal likelihood, reducing the tendency of unconstrained models to converge toward preferred but misleading solutions. We test this framework on 539 stars in IC2602, the Tucana-Horologium Association, Pisces-Eridanus, and GroupX, with independently reported and manually vetted rotation periods. This benchmark evaluates GP hyperparameter interpretability and automated period recovery with minimal human intervention. We compare regularized and unregularized models across several regularization strengths, {\lambda}, using literature agreement, sector-level diagnostics, and consistency across TESS sectors. Relative to the standard GP likelihood, regularization improves successful rotation-period recovery by an average of 7%. It also generally reduces the median absolute fractional deviation of periods across sectors, showing that the improvement is not limited to catastrophic failures but also mitigates smaller systematic errors. Regularization is particularly beneficial for non-sinusoidal or evolving modulation, where unconstrained GPs may recover harmonics or spurious timescales. These results show that likelihood regularization and cross-sector consistency are practical diagnostics for assessing when GP-based rotation periods are robust.
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All authors Leslie Moranta, Jonathan Gagné, Jacqueline K. Faherty, Mark Popinchalk, Jason Lee Curtis, Johanna M. Vos, Alexandrine L'Heureux, Andrew Ayala, Eleanor Johnson, Dawn McCullough, Nicole Munoz, Hannah Park, Xue Weng, Livia Poliquin, Ilhem Lazizi

Instrumentation and Methods for Astrophysics · Cross-listed from gr-qc

Unsupervised Deep Learning Method for Clustering KAGRA O3GK Transient Noise Data

Yubin Kim, Kihyun Jung and Kyujin Kwak

The advent of ground-based gravitational wave detectors has significantly improved the detection of faint gravitational wave signals. However, these detectors are affected by various types of transient noise, known as glitches, which can mimic true gravitational wave signals and limit detector sensitivity. Classifying glitches according to their time-frequency characteristics not only facilitates a deeper understanding of their origins, but also supports their mitigation on data to maintain data quality. While supervised machine learning methods are commonly employed for glitch classification, they require the labelling of training datasets obtained through manual annotation, a process which is costly and not scalable for evolving detectors. In order to address this challenge, the present study investigates unsupervised deep learning methods for dimensionality reduction and clustering of glitch spectrogram images. In this study, three distinct approaches are applied and compared using data from the KAGRA detector's O3GK run. The findings of this study demonstrate that deep learning-based feature extraction significantly enhances the clustering performance compared to traditional machine learning methods. This study presents an initial analysis of the KAGRA glitch dataset using unsupervised deep learning, highlighting the potential of this approach for efficient and scalable glitch classification in future observation runs.
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Instrumentation and Methods for Astrophysics · Cross-listed from astro-ph.CO

Chebyshev interpolation in Einstein-Boltzmann codes

Herman Sletmoen

Einstein-Boltzmann codes compute theoretical predictions of cosmological models and rely heavily on interpolation in their independent variables: time $\tau$, wavenumber $k$ and multipole $\ell$. We give a practical summary of interpolation with Chebyshev polynomials, which converges rapidly for smooth functions and thus pairs naturally with approximation-free Einstein-Boltzmann codes. By solving the perturbations and line-of-sight integrals at Chebyshev nodes in $k$ and $\ell$, we show that Chebyshev polynomials interpolate to higher precision than traditional cubic splines from fewer explicit solutions. On a set of example spectra for matter and the cosmic microwave background (CMB), we find up to four orders of magnitude lower interpolation error using the same number of points. For a typical CMB temperature spectrum computed with interpolation in both $k$ and $\ell$, Chebyshev polynomials converge to $10^{-4}$-$10^{-5}$ relative error with only 50-80 points per variable, while cubic splines approach $10^{-4}$ error with 200 points, translating to a $2.5\times$-$4\times$ speedup. The exact improvement depends on the target function and is generally more dramatic at high precision levels. Standard Chebyshev $\ell$-interpolation needs line-of-sight integrals generalized to non-integer $\ell$, but we show a way to avoid this by rounding the nodes to integers. Chebyshev interpolation is implemented in SymBoltz, which is available at https://github.com/hersle/SymBoltz.jl.
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Instrumentation and Methods for Astrophysics

NIRC2-Pol: First Light of Near-Infrared Polarimetry on Keck II

Briley L. Lewis, Manxuan Zhang, Maxwell A. Millar-Blanchaer et al. (+21 more)

NIRC2, the Near Infrared Camera 2 on the Keck II telescope, was recently upgraded with a new suite of polarimetric observing modes. The new polarimetry modes (referred to as NIRC2-Pol) open up a wide range of new studies, including investigations of exoplanets, the Galactic center, active galactic nuclei, and solar system objects. The new modes enabled by the upgrade span the 1.1 to 4.1 micron range (i.e. J through L' bands) and include imaging polarimetry, coronagraphic imaging polarimetry, and spectropolarimetry. NIRC2-Pol is unique, as Keck II is the largest telescope (10 m) on which AO-fed infrared polarimetry capabilities are available, one of few with L' polarimetric imaging, and the only one where there is both a polarimetric mode and a vortex coronagraph. Here, we introduce the design of NIRC2-Pol, its capabilities, and its current operational status. We also present its first on-sky results: the first L' polarimetric images of the AB Aurigae circumstellar disk. These images more clearly reveal the disk's iconic spiral arms than previous L' total intensity imaging.
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All authors Briley L. Lewis, Manxuan Zhang, Maxwell A. Millar-Blanchaer, Eduardo Marin, Jayke S. Nguyen, Carlos Alvarez, Jaren N. Ashcraft, Mahawa Cisse, Charles-Antoine Claveau, Greg Doppmann, Michael P. Fitzgerald, Matthew Freeman, Trisha Hammen, Ryan Hersey, Nemanja Jovanovic, Scott Lilley, Jessica Lu, James E. Lyke, Keith Matthews, Dimitri Mawet, William Melby, Thomas McIntosh, Max Service, Jacob Taylor

Instrumentation and Methods for Astrophysics

A high-isolation wideband channelizer for MKID readouts: a custom HLS implementation on RFSoC

Alberto Hernandez Fernandez, David Diaz Martin, Jose Javier Diaz Garcia et al. (+4 more)

We present a high-performance channelizer for Microwave Kinetic Inductance Detectors (MKIDs), designed to mitigate spectral leakage and scalloping loss through a 50% overlapping polyphase filter bank (PFB). The design is implemented on a Xilinx Zynq UltraScale+ RFSoC ZCU111 using a custom design - primarily in Vitis High-Level Synthesis (HLS), with the time-critical output serializer and glue logic in VHDL - that processes a 4.096 GSPS input stream with a per-branch super-sample rate (SSR) of 16. Rather than relying on aggressive 512 MHz clocking and vendor IP cores, our split-path architecture computes the delayed and non-delayed polyphase branches concurrently, so that the bulk of the channelizer operates at a robust 256 MHz while a single 512 MHz subdomain is confined to the BRAM-to-FFT section. This architectural parallelism enables a deep 16-tap prototype filter that doubles the filter depth of comparable high-speed systems and substantially improves channel isolation. We report the complete internal architecture of the reordering engine that implements the overlap, including two implementation hazards not documented in prior art: a pipeline-stage skew affecting state toggles in HLS, and the state-preservation requirements of a restartable design. The 2/1 overlapped channel response is validated in simulation - recovering the ~3.9 dB scalloping loss of a critically sampled channelizer to below 0.1 dB across the full 2 MHz channel - and characterized systematically with a 100-tone batch frequency sweep, while the parent readout system has been operated cryogenically with an MKID array in an adiabatic demagnetization refrigerator (ADR), identifying individual resonators in total darkness. The result is a resource-efficient, high-isolation benchmark for wideband frequency-division-multiplexed readouts.
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All authors Alberto Hernandez Fernandez, David Diaz Martin, Jose Javier Diaz Garcia, Roger John Hoyland, Luis Fernando Rodriguez Ramos, Diego Portero Rodriguez, Silvestre Rodriguez Perez

Instrumentation and Methods for Astrophysics

Forward modelling coronagraphic images with a fully physical, differentiable digital twin of MagAO-X: first laboratory results

Matthijs Mars, Sebastiaan Y. Haffert, Louis Desdoigts et al. (+10 more)

Post-processing of high contrast imaging data relies on an accurate model of the stellar point spread function (PSF). Current techniques build this model from the science images themselves, using observational diversity (e.g., angular, spectral or polarimetric diversity), which can cause self-subtraction of the companion signal and constrains the observing strategy. Telemetry-based forward modelling instead builds the stellar PSF model from wavefront sensor data that is already recorded during the observation. The wavefront sensor measures the coherent starlight and can therefore be used to create a PSF model that only models the stellar light and does not reproduce the incoherent light of a companion. We present a fully physical and differentiable digital twin of the focal plane low-order wavefront sensor (FLOWFS) and the coronagraphic science beam of the MagAO-X instrument, implemented in dLux, and calibrate it on laboratory data. When fitted directly to the science images, the model reproduces the coronagraphic PSF down to the photon and read noise floor of the data. When instead forward modelled from the FLOWFS telemetry alone, the residuals reach $6\times10^{-5}$ of the stellar peak at $5\ \lambda/D$, a factor of 5 below the raw contrast, with the remaining residual set by how well the wavefront estimate transfers from the FLOWFS branch to the science branch of the model. An injected companion at $5\ \lambda/D$ with a peak contrast of $10^{-3}$ is recovered without measurable self-subtraction. We discuss the model improvements currently under development and the path towards on-sky validation.
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All authors Matthijs Mars, Sebastiaan Y. Haffert, Louis Desdoigts, Joseph D. Long, Rico Landman, Jared R. Males, Laird M. Close, Kyle Van Gorkom, Olivier Guyon, Alexander D. Hedglen, Sandrine Juillard, Jennifer Lumbres, Lauren Schatz

Instrumentation and Methods for Astrophysics

NEXT: The Netherlands EXoplanet Testbed I. Goals and opto-mechanical design

Rico Landman, Sebastiaan Haffert, Louis Desdoigts et al. (+7 more)

We report on the goals, design, and ongoing development of the Netherlands EXoplanet Testbed (NEXT), a high-contrast imaging testbed under construction in Leiden. NEXT is designed to develop and validate technologies and algorithms for extreme adaptive optics (XAO) and coronagraphy at the performance levels required by the next generation of high-contrast imagers on the Extremely Large Telescopes (ELTs) and future space observatories. All powered optics in the common path are custom off-axis parabolas, making the bench fully reflective up to the science cameras, and it operates from the visible to the near-infrared (500-1800 nm). It combines a woofer-tweeter XAO module, using an ALPAO woofer and a Boston Micromachines kilo-DM as tweeter, with a coronagraphic arm that supports common coronagraph architectures and focal-plane wavefront control for dark-hole digging, and reserves space for a suite of wavefront sensors. The design targets a raw contrast of $10^{-7}$ (goal: $10^{-8}$) at $5\lambda/D$ and 800 nm. We present the opto-mechanical design of the testbed, the key trade-offs made to reach these contrast levels, and Fresnel-propagation simulations of its predicted performance.
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All authors Rico Landman, Sebastiaan Haffert, Louis Desdoigts, Matthijs Mars, Dhwanil Patel, Daniel Smith, Remko Stuik, Adam Taras, Elena Tonucci, Yinzi Xin